Diseases of Game BirdsPart 4 - Diseases from 10 days to 7 weeks of age

Disease incidence in gamebirds, 11 to 42 days
old

Introduction. Many of the diseases seen
in the first 10 to 12 days of life may also be encountered in the
next growing phase of the game bird. If the main detail of one
specific disease is in a previous bulletin it will be marked and so
you should refer to that as well.

Aspergillosis

Cause.
Infection of the respiratory tract with various fungi, mainly of
the Aspergillus family (Fig 1).
Damp shavings and straw are particular sources. Most commonly
associated with poor air circulation in the brooder hut or night
shelter. Partridge seem to be affected more often that pheasants,
simply because of the amount of dust they create by their panic
response to the slightest little movement within the house.
Remember that the fungi are the agents of Farmer's Lung in
humans.

Fig 1. Fungal hyphae from air sacculitis under
microscope

Signs. Birds
in this age group tend to present with severe respiratory signs.
They are usually very unwilling to move and if they do may well
fall over as a consequence. They stretch their necks to try to get
easier passage of air into the lungs and air sacs. With secondary
bacterial infection mortality rates may be high.

Post mortem.
The lungs may well be fairly solid, but the most outstanding sign
is the very great thickening of the walls of the air sacs. These
may also have a creamy cheesy appearance. (Fig 2 &
3)

Fig 2. Air sacculitis

Fig 3 Air sac with fungi clearly
showing

Treatment.
There is no specific treatment available for use. It may be
dangerous to use anti-bacterial drugs as it may create an
environment in which the fungi can super-proliferate. Iodine
preparations have been used. The most important thing is to reduce
the spread amongst the other birds. This can be done by regular
cleaning and disinfection of the drinkers and feeders. Improving
the ventilation is critical. Replacing contaminated litter is
advisable, if possible. If not, it is possible to spray the
spreading with anti-fungal agents, but this must be carried out
with great care and may be of limited value.

Ascarid worms

Cause. Large
roundworm, 50-80mm long. Mainly found in the upper intestines of
partridges.

Signs. Large numbers will cause unthriftiness and may cause
obstruction of the intestines resulting in death. (Fig
4)

Fig 4 Ascarid worms in Red Legged
Partridge

Birds can be reared quite
happily with a substantial burden, but we have seen significant
mortality very soon after moving from the rearing field to release
or holding pens.

Treatment.Flubenvet® is the licensed wormer for use in game birds.
Other wormers are used, but have no licence for game
birds.

Avian
encephalomyelitis

See description in
previous bulletin 1 to 10 days old

Avian Influenza(See also in
0-10days bulletin)

Cause.
Various influenza viruses. Can be transmitted to Man.

Signs.
Variable, depends on Pathogenicity of the virus strain.

Treatment.
None presently available for flocks of game birds

Control.
Don't allow it in!

Capillaria(Hair
worms)

More commonly seen once birds
have been released, but if the rearing site is contaminated with
eggs, may be seen with devastating effects, usually from August
onwards.

Cause.
Nematode worm, Capillaria contorta. Recent
re-classification and some species are now referred to as
Eucoleus. Are very thin and long (0.1 by 60mm).
(Fig 5) (Very difficult to see with the
naked eye.

Fig 5 Capillaria - whole
worm

Signs. Poor
growth and feathering. Mortality can be very high in young birds
with heavy infestation in the crop. They burrow in the gut wall
causing weakness, weight loss, difficulty swallowing, diarrhoea and
death.

Fig 6 Capillaria - egg

Post mortem
Diagnosis fairly straightforward, as the eggs have a characteristic
"plug" at each end (Fig 6). It is often
easier to identify the eggs than the intact worm because of its
burrowing nature.

Treatment.
Standard worming regimes may be sufficient, but sometimes a tougher
approach has to be taken with veterinary advice.

Coccidiosis(Cocci -
pronounced "coxy")

Cause. An
intra-cellular parasite of the intestinal tract of the genus
Eimeria.

Fig 7 Coccidial oocysts

Fig 8 Caecal plug in Red Legged Partridge caused by
coccidiosis

Signs. The
disease is characterised by enteritis and diarrhoea, and is of
great importance in the game bird and poultry industry. Even
subclinical disease will still cause economic losses. Coccidia are
host specific, meaning they only infect one species of bird and are
site specific, meaning every species of coccidiosis colonises only
a certain part of the intestinal tract Thus Pheasant cocci does not
affect Partridge and vice-versa. Oocysts, tough hard shelled bodies
(Fig 7) containing infective stages of
cocci, are passed out in the droppings and ingested by other birds
via contaminated drinking water and feed. Once ingested the
coccidia go through a complex life cycle of several stages in the
intestinal cells causing damage and disease. The life cycle can be
as short as 7 days. Clinical signs include depression, reduced
appetite, ruffled feathers, vent pecking, diarrhoea (sometimes
containing blood), dehydration, weight loss and death. Red Leg
Partridges are very susceptible and sudden deaths (in large
numbers) are not uncommon. Grey partridges are seldom affected by
coccidiosis.

Post mortem.
Depending on the species of Eimeria involved there can be
lesions seen in various parts of the intestine. Perhaps the most
obvious is the caecal pug seen in caecal Coccidiosis in Red Legged
Partridge (Fig 8). In pheasants intense
inflammation of the intestine is more commonly seen.
(Fig 9)

Fig 9 Coccidiosis: Damage (red spots) to the lining
of the intestine (mucosa)

Prevention.
The only product licensed in game birds is the coccidiostat
Avatec®. This is usually included as a "standard" in all game feed
for birds up to 13 weeks old.

Treatment.
There are two major products used in the UK. Baycox® is licensed
for use in poultry and so can be used on the prescribing "cascade".
Amprolium is not licensed, but may be used under special licence if
there are signs that the licensed product is not having the desired
effect. These products may only be prescribed by a
veterinary surgeon.

Control.
Oocysts are very tough and can survive in the environment for a
year. An ammonia based product (such as Oocide®) is needed to
destroy them. It is almost impossible to prevent contact with
oocysts. The best thing is to try and influence the balance between
developing immunity and weight of challenge. Challenge can be
reduced by the use of coccidiostats in feed, attention to hygiene
(especially round drinkers and feeders) and avoiding re-use and
overstocking of pens. The trick is to use a coccidiostat in feed at
such a level that it allows birds to develop immunity before they
are released, without them getting ill.

Fig 10. Gapes. Eggs from crop
smear

Fig 11. Gapeworms in the trachea

Gapes

Cause.Syngamus trachea, commonly known as gapeworm, is the most
important worm in game birds. More likely to be a problem with
birds after release.

Life cycle.
The adult worms live in the trachea (windpipe) of game birds,
poultry and several other birds such as rooks, crows and
starlings, causing Gapes. The produced eggs are coughed up,
swallowed and pass out in the droppings. An infective larva
develops inside the egg. Birds may be infected by eating the eggs
(Fig 10) or larvae, or by eating
earthworms that have themselves eaten eggs or larvae. The larvae
form a cyst in the muscle of the earthworm and may remain infective
for up to 4.5 years, thus forming a reservoir of future infection.
When swallowed by the bird the larvae migrate through the body or
bloodstream to the trachea via the lungs. Here they rapidly grow
into adult worms. The worms suck blood and can cause weight loss,
anaemia, weakness and reduced egg production.

Signs.
Respiratory signs, such as coughing and "snicking", are caused by
irritation of the trachea by the worms. Head shaking after snicking
is also a common sign. Death occurs by suffocation when worms block
the airways. Partridges seem to be especially susceptible and
mortality can be rapid and high.

Post mortem.
The adult worms are easily seen in varying numbers in the trachea
(windpipe) (Fig 11).

Treatment and
Control. These two go hand in hand. It is virtually
impossible to stop the birds being exposed to the worm egg, because
of the wide variety of hosts. On the rearing field the risk can be
reduced by ensuring wild birds have as little access as possible to
the birds on the field.

Flubenvet® is the licensed
wormer for use in game birds. Other wormers are used, but have no
licence for game birds. Flubenvet® is incorporated in feed and is
most commonly done for you at the mill. You do need a veterinary
prescription (MFS) for this. This is another part of the Veterinary
Health Plan you should draw up with your vet at the start of the
season.

Hexamita/Spironucleus

Cause.Hexamita, now called Spironucleus, is a single
cell organism, a protozoon, only slightly bigger than
bacteria.

Signs. Acute
disease characterised by enteritis with foamy/watery diarrhoea.
Disease usually occurs in birds under 9 weeks of age. Symptoms
include chilling, huddling, ruffled feathers, stilted gait (so
called 'moon walking') and watery or foamy diarrhoea. Infected
birds dehydrate rapidly and lose weight. They tend to throw food
out of hoppers. Death occurs due to loss of electrolytes. Mortality
may be as high as 75-90% in young birds!

Post mortem.
Birds are emaciated and very dehydrated (Fig 12).
The contents of the caecum (blind gut) are often yellow varying
from pasty to very liquid consistency. Very high numbers of highly
motile organisms can be readily identified in scrapings from the
intestinal wall of affected birds. The organism may die soon after
the death of the bird; therefore it is very important to present
fresh birds, or even better, sick birds, to get an accurate
diagnosis. Birds that survive will remain carriers and shed
parasites with their faeces. The incidence of disease increases
when successive hatches are placed in infected pens. It is also
very simple to carry infection from pen to pen on dirty
boots.

Fig 12. Hexamita. "Razor keel" caused by
disease

Fig 13a. Hexamita. "typical" yellow frothy
dropping

Diagnosis. Popular
mythology is that you can diagnose this infestation by just looking
at the droppings. Sadly other intestinal diseases also produce the
same sort of yellow, frothy or custard like faeces (Fig
13a), which, in any case, are not consistently the
case with Hexamita
(13b).

Fig 13b. Hexamita - Opened caeca (blind gut) from
one bird. Demonstrating that there is no "typical" colour to the
content and thus the dropping.

Spread. Can
spread between pheasants and partridges. It is often found together
with other parasites such as Trichomonas and Coccidiosis.
Transmission occurs via direct bird-to-bird contact and ingestion
of droppings, contaminated feed or water. Cysts have fairly
recently been identified in the mucus generated by the lining of
the intestine.

Treatment. There are no licensed
products for the direct treatment of Hexamita. Various antibiotics,
together with electrolytes are frequently used with varying
success. These are given both in liquid form and in feed. Again, if
used in feed you do need a veterinary prescription (MFS) for
this.

Necrotic enteritis and Ulcerative
enteritis

(Examples of Clostridial
bacterial infections)

Cause.
Necrotic enteritis was first described in poultry in the 1960's and
has subsequently been reported pretty much all over the world. It
is defined as being related to infection with Clostridium
perfringens (old name Clostridium
welchii).

Signs. Most
commonly the disease is seen in poultry being reared on litter. It
is often associated with damage to the intestinal wall caused by
other factors, such as coccidiosis. We have seen a similar gross
pathology in Red Legged Partridges. Clostridium
perfringens and several other clostridial species were
isolated from affected birds. Coccidia were an incidental finding
in some cases, but certainly not in all. The level of coccidial
disease was regarded as being high enough to cause disease, but not
the mortality rates seen in these cases. We have seen several
episodes of ulcerative enteritis in Red Legged Partridge in the
last few years.

Post
mortem. Ulceration in the wall of the caecae is as a
regular feature (Fig 14)Obvious signs of inflammatory change close to the junction of
the small intestine with the blind gut (caecum). Ulcerative
Enteritis has been described for over 100 years, and was initially
seen in quail (hence its nickname Quail disease). It has also been
seen in grouse, pigeons, chicken, and pheasants.

Source.
Clostridia are natural inhabitants of soil. They persist as spores.
It is only when there is a trigger factor or factors, such as
moving, hard weather, exposure to other intestinal injury (e.g.
coccidiosis) that problems arise.

Treatment.
In the first cases amoxycillin in water. Early bacteriology
suggested that the organism found were resistant to this.
Consequently it was changed to a fluoroquinolone, but the birds did
seem to do better on the first choice treatment.

Pseudomonas

Cause.
Bacterial infection with Pseudomonas organism. Often a
consequence of poor hatchery hygiene.

Signs. Can
be seen in early rear or later. May be associated with high
mortality. Sometimes presents as blindness with infection clearly
visible inside the eye.

Treatment.
Early diagnosis is vital, when antibiotics will help. Those with
blindness are unlikely to show a very good response, but mortality
can be reduced in others.

Ricketts(See also in
0-10 days bulletin)

Cause.
Calcium or Vitamin D deficiency. Generally seen in birds slightly
older than 10 days, but in severe cases may be younger.

Signs. Birds
usually present with lameness and inability to walk or stand. Limbs
may be bent.

It is because is usually
dietary that it is seen at 2 to 4 weeks old. If the egg itself is
very thin shelled, or the resorption of Calcium from the shell to
the chick in late stage incubation is impaired, they may
theoretically be born affected.

Streptococcosis

Cause.
Infection with Streptococcus family of bacteria. Route may
be by damage to the skin (e.g. feather-pecking, exposed wire ends),
ingestion or aerosol.

Signs. Most
commonly presents as acute mortality in otherwise well growing
younger birds. At post mortem an intense septicaemia can be seen
throughout the body cavities.Bacteria may even be demonstrated in
blood smears or bone marrow.

Treatment.
Luckily most streptococci remain sensitive to many antibiotics,
mainly of the penicillin family.

Prevention.
Basic hygiene and avoiding risk of injury.

Yersinia
(Pseudo-tuberculosis)

Cause.
Infection by Yersinia pseudotuberculosis

Signs. Seen
occasionally in Red Legged Partridge. Signs are very variable,
varying from ill thrift to sudden death. Usually goes on for about
2 or 3 weeks. Will depend on which organs are most
affected.

Post mortem.
Widespread lesions can be seen in all the major organs. As its name
suggests very difficult to tell apart from Avian tuberculosis.
Absolute diagnosis depends on culture of the organism from affected
birds.

Treatment.
Of little value. Culling and thorough cleansing of the
accommodation is most likely the best plan. No vaccine is currently
available. As is so often the case, a vaccine for Gamebirds is
unlikely to be developed because of the small potential
market.

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